A semiconductor device, such as a metal-oxide-semiconductor field-effect transistor (MOSFET) device and/or the like for use in an electronic device or the like, is fabricated using a plasma etching technique. An etching process, using plasma, of a semiconductor substrate (hereinafter referred to simply as “substrate”) requires process uniformity across the substrate surface for yield improvement with respect to the substrate. To achieve uniformity in etch profile across the substrate surface amid the progress of dimension reduction in recent years, control of ions bombarding the substrate from plasma is becoming more important.
Conventionally, examples of known plasma processing technology for use in fabrication of a semiconductor device include an apparatus for etching with high accuracy a film structure having a stepwise surface as described in PTL 1, which is a plasma processing apparatus including a vacuum vessel, a lower electrode disposed in a processing chamber in the vacuum vessel to mount a wafer on top thereof, a plurality of bias application units of different frequencies for supplying radio frequency (hereinafter referred to simply as “RF”) power to produce a bias potential on the lower electrode, a gas supply means for feeding a reactive gas into the processing chamber, an electric-field providing means for providing an electric field to generate plasma in the processing chamber, and a regulation unit for regulating energy distribution of ions, in the plasma, bombarding the wafer by means of the RF power. In addition, the regulation unit is configured to control the output ratio (mixture ratio) between the bias powers having a plurality of frequencies generated by the bias application units, thus to change the energy of ions bombarding the wafer and the distribution thereof independently.
Moreover, examples of known technology to control energy of ions bombarding the wafer include, as described in PTL 2 for example, application of an RF voltage amplitude-modulated by a plasma processing apparatus having a cathode-coupling configuration, and application of an RF voltage frequency-modulated by a plasma processing apparatus having an anode-coupling configuration.